Airplane engine mounting



July 10, 1945. R. 5. mm 7 2,380,274

AIRPLANE ENGINE MOUNTING Filed Nov. 4, 1940 5 Sheets-Sheet 2 20 ROLLAND 5.TROTT J51 WW 6. :1

1%. 11mm Aw ATTORNEYS July 10, 1945. I R. S. TROTT 2,380,274

AIRPLANE ENGINE MOUNTING Filed Nov. 4, 1940 3 Sheets-Sheet 3 IN VEN TOR.

Patented July 10, 1945 AIRPLANE ENGINE MOUNTING Rolland S. Trott, Denver, 0010.; Eleanor J. Trott executrix of said Rolland S. Trott, deceased Application November 4 1940, Serial No. 364,185

7 Claims. (01. 248) My invention relates to mountings for mounting airplane engines in airplanes.

In my former invention disclosed in Reissue Patent No. 22,403, December '7, 1943, a front and a rear mounting was provided. The front mounting was a metallic pivotal mounting, which front metallic mounting. provided for oscillation of the engine unit about an axis which passes through the center of the propeller hub, through the center of mass of the engine unit, and through the center of the rear mounting. My former application covers the. present invention broadly, but though this is so, my former invention did not disclose the specific construction of my present invention. Though my former application covers an engine mounting with front and rear mountings locating the axis of oscillation so it will pass through the center of the propeller hub and through'the quite adjacent center of mass of the engine unit and through the rear mounting, the specific form of engine provided in this present application, in which the center of mass of the propeller and the center of mass of the engine are quite broadly separated, was not disclosed; and the rear mounting didnot specifically include the same combined metallic pivotaland cushioned construction used in the front mount- While in my former application my invention was shown as applied to radial engines, n disclosure was made of my invention as applied to in line engines, in which the centerof mass of the engine is longitudinally more remote from the propeller; and while my invention was shown in an engine construction in which the center of mass of the engine is normally on the crankshaft, there was no illustration ofmy invention applied to engines in which the center of mass is normally either above or below or to one side of the crankshaft axis.

Also my former application did not teach what r to do in a radial engine in which the center of mass is not exactly on the crankshaft axis. And, though the main principles and constructions of my former application apply equally well to inline engines and to radial engines, no specific form of in-line engine installation was shown, nor

wa there any specific instruction as to how to mount radial engines whose centers of mass were not in the crankshaft axis.

In this present application, an in-line engine is illustrated; the rear as well as the front mounting is metallic and pivotal and cushion supported, and the axis of oscillation passes not only through the center of mass of the engine, but also through the center of mass of the propeller, and through both the front and rear mountings, even though the rear mounting may not be in the crankshaft axis. That is, even though in some engine units neither the center of mass of the propeller nor of the engine may be in the crankshaft axis, nevertheless, the axis of oscillation must pass through both the centers of mass.

In this present application the longitudinally extending torque spring illustrated in my former application may be employed, but also other optional, hydraulic, frictional, metallic and nonmetallic torque cushioning means, accomplishing the same results in general, are illustrated, and any or all of which may be used in place of or in addition to the torque construction shown in my former application. Any or all of these torque resisting constructions may be used in combination to obtain the exact torque cushioning results needed for any specific installation. In my present invention, an in-line engine is illustrated in various ways, and though only a single row in-line engine is shown, it is to be understood that a V, an X, or any other form or type of in-line engine may be employed in this invention, and with the resulting various locations of the centers of mass of both the propeller and the engine.

In this invention the front metallic pivotal mounting is back of and adjacent the propeller in the ordinary plane in which the propeller is at the front end of the engine. (If a pusher type of propeller is used, this front mounting is then the rear mounting, and is located in front of the propeller, as any mechanic will understand.) This front metallic mounting positively fixes the axis of oscillation at the front of the engine so it passes through the center of mass 'of the propeller; located at the center of the propeller hub.

The axis of oscillation is to pass through the center of mass of the propeller, whether a geared propeller or an ungeared propeller is employed. The propeller is, in effect, a flywheel and its center of mass must not be moved by the engine oscillation.

This front metallic pivotal mounting is carried on the engine mounting framework through supporting the front of the engine, as anyone versed in the art will understand.

The rear metallic mounting in this present case is located concentric with the axis of oscillation that passes through the center of mass of the propeller and through the center of mass of the engine. It will be noted that this rear mounting location will therefore change depending upon the type of in-line engine that is used. In the radial type engine this rear mounting will be concentric with the crankshaft if the engine center of mass is on the crankshaft axis, as shown in my former patent application. That is, an upright in-line engine will have a center of mass slightly higher above the crankshaft than will a V-type of in-line engine; and this will naturally locate the rear mounting slightly higher than the rear mounting of a V-type of engine; and both of these types will have rear mountings higher than a radial type of engine.

An inverted type of in-line engine will have the center of mass below the crankshaft level and a rear mounting lower than the radial type of enine illustrated in my former application.

It is generally assumed that the center of mass of a radial type of engine is in the crankshaft axis, in which case the rear mounting will be concentric with the crankshaft axis. However, when the plomb bob test, described hereinafter, is applied it will be found that very few radial engines can, for perfect results have a strictly concentric-with-the crankshaft rear mounting. But, in any case, the final situation will be the same in that the oscillation of the engine unit will take place in perfect balance with the axis through both centers of mass so the oscillation will create no new forces that will vibrate the airplane.

All of this will be more clearly seen by reference to the drawings, in which:

Fig. 1 shows an upright S-cylinder engine, with the propeller concentric with the crankshaft, the center of'mass of the engine above the crankshaft and the mountings located so the axis of oscillation passes through the center of the propeller hub, which is the center of mass of the propeller, through the center of mass of the engine, and through the rear mounting which is above the crankshaft. The engine may thus oscillate in perfect balance. Redistribution of the weight of the parts of the engine, or its parts or accessories will not change this condition, since in any case the axis of oscillation still must pass through the points above mentioned;

Fig. 2 shows the same construction as Figure 1, but with the engine inverted, that is, upside down. The center of mass of the engine is thus below the level of the crankshaft. This brings the rear mounting below the crankshaft, but still the engine may oscillate in perfect balance;

Fig. 3 shows the Figure 2 engine-and position, but the. propeller is driven through gears or other reduction means. Nevertheless, the axis of oscillation passes through the center of mass of the propeller, through the center of mass of the engine, and through the rear mounting, so that the engine may oscillate'in perfect'balance. The reduction means is shownzextending upward above the crankshaft, though of course, with the engine either upright or inverted, the reduction mean may extend either upward above the crankshaft or downward be I W the crankshaft. In Fig. 3 neither the center of mass of the propeller nor of the engine is in the crankshaft axis,

and yet the entire unit may oscillate in perfect balance;

Fig. 4 shows the same engine, upright, and with the reduction means extending upward above the crankshaft. The axis of oscillation is substantially parallel to the crankshaft, but the engine unit still may oscillate in perfect balance, even though neither the center of mass of the propeller nor of the engine is in the crankshaft axis;

Fig. 5 shows the same upright engine, but with the reduction means extending downward below the crankshaft. Though this changes the angle of the axis of oscillation, the engine may still oscillate in perfect balance, even though neither the propeller center of mass nor the engine center of masslies in the crankshaft axis;

Fig. 6 shows one form of metallic pivotalfront mounting supported on rubber cushions, which in turn are supported on the supporting framework carried by the plane;

Fig. 6' is a fragmentary section of the cushions of Fig. 6;

Fig. 'l and Fig. 8 show a simple form of metallic pivotal mounting supported on a cushion which is primarily intended for the rear mounting of the engine, but which, if desired, may be used to support the front of the engine, and which may be carried in'a cushion-supported cross member, or on a cross member rigidly .car ried by the plane supporting framework. This mounting contains inner and outer metallic sleeves that are integral'with the rubber'of the mounting either by vulcanizing or otherwise. No torque and no thrust is taken by this mounting.

Fig. 9 shows a rear mounting, with inner and outer metallic members that are provided with splines whereby-the torque of the engine may be taken from the engine to the plane;

Fig. 10 is a fragmentary sectional viewof the splined fomr of rear mounting shown in Fig-9 and engaged with the engine and the supporting in addition thereto;

Fig. 15 shows the simple form of rear mounting frame-work support for the simple form of rear mounting shown in Figs. '1 and 8;

Fig. 16 shows a fragmentary side view of the rear mounting with a controllable hydraulic torque-resisting means having independent manually operated and throttle-operated control means;

Fig. 17 is an end view of Fig. 16; and

Fig. 17' shows a detail of a modified form of torque arm.

It will be noted that no supercharger either at one end of the engine or in any other location is shown, nor is a starter of any kind, nor carburetor, nor intake manifold, nor exhaust manifold, nor are various other necessary parts of a complete engine unit shown. It is, however, to be understood that the engine is to be equipped with all necessary or desired parts or accessories and that the engine as illustrated is to be considered representative of an engine in its complete and fully equipped condition. The center of mass indicated on the drawings is for this complete and fully equipped engine.

Fig. 1 illustrates an in-line engine whose center of mass I, is above the crankshaft 2; that is, above its level. The axis of oscillation 3, passes through the center of mass I, through the center of the propeller hub 4, that is, the center of mass I, and through the center of the rear mounting 5. It should be noted that the center of the front mounting engine hub 6 is slightly above the crankshaft 2, which is required if the axis of oscillation 3 is to be located to pass through the center of the propeller hub 4.

If the axis 3 does not pass through the center of the propeller hub 4, then as the engine oscillates the tendency is to move the rotating propeller by the oscillation, and this will produce vibration. For, the propeller is in effect a flywheel which always tends to revolve about its own center of mass I' at the center of the hub}.

The front hub 6 of the engine is located, so that it locates the axis 3 to pass through the center of mass I of the pro eller and through the center of mass I, of the engine. The engine hub 5 is supported on the cross member I, which will be described more in detail in connection with Fig. 6 here below.

The rear of the engine is supportedon the rear mounting extension 8, which is either bolted or otherwise properly attached to the engine, or

which may, if desired, be made integral therewith. This extension 8 may be built of sheet metal structure, or may be of skeleton or any other form or type of construction, so long as its rear end is cylindrical to properly be supported in the rear mounting 5, which is above the crankshaft 2.

Two lugs 9, 9, are fixed, to or integral with an extension 8 of the engine itself, and, through the wrist pin I0, locates the front end of the torque spring II. The wrist pin III may be locked in the lugs 9, 9, by cotterpins or screws or in any other usual or. proper manner, so that though the wrist-pin Il] may be removed. it will, unless removed, be permanently held in place. A rubber bushing (not shown) may, if desired, be used in the eyes of the torque spring II.

The torque spring II is twisted QOdegreeS between its ends and itsrear end is located by the wrist pin I2, which is 'to be properly mounted and locked in lugs similar tothe lugs 9, 9, but carried by the fusilage or framework of the plane in which the engine is mounted; This will be described more fully in connection with Figs. 16 and 17.

The rear mounting 5 iscomposed of the metallic inner sleeve I3, therubber cushion I4 and the metallic outer sleeve I5. Details of this rear mounting 5 will be seen in Figs. 7 and 8. It will be noted that the axis 3 passes through the center of the rear mounting 5, and is so maintained by the metal pivotal bearing between the inner sleeve I3 and the cylindrical rear end of the extension 8.

The metal front engine hub 6 and the metal cross member 1, insures that any oscillation taking place at the front must be about the axis 3,

and this axis passes through the center of mass of the propeller and the center of mass I,' of the engine.

It will now be seen that as the engine oscillates, the, axis of oscillation 3 is located by both mountings so that it passes through the center of the .cross member I and the center of the rear mounting 5.

Thus the engine is forced to oscillate in perfect balance, so that the oscillation will create no new forces whatever, and the oscillation will have no vibrational effects whatever. The metallic front and rear mountings insure this oscillation in perfect balance.

The torque spring II not only resiliently resists the torque cushioning oscillation of the engine, but it also acts to locate the engine longitudinally; and the rubber bushings for the two wrist-pins, if the bushings are used, will act to transmit the thrust of the propeller resiliently from the engine to the plane.

Fig. 2 shows substantially. the same structure as Fig. 1 except that instead of an upright engine, an inverted engine is used. That is, the engine shown in Fig. 2 is the Fig. 1 engine turned upside down and with the necessary changes made for this new engine position. For example, the center of mass I is below the crankshaft 2, the rear mounting 5 is below the crankshaft 2, and the cross member I is centered slightly below the crankshaft 2. However, in results, the two structures are the same, in that they will both oscillate in perfect balance, and neither the propellers center of mass nor the engines center of mass will be moved transversely as'the engine oscillates. Of course, if the propeller is slightly out of balance, the cushion mounting of the cross member I, or the cushion mounting of the mounting 5, if it is used,-at the center of the cross member I, or both of them, if they are both used, will cushion this out-of-balance and tend to smooth out the vibrations due to unbalance.

Fig. 3 shows an inverted engine such as shown results in oscillation in perfect balance, as in the Figure 1 and Figure 2 constructions.

Fig. 4 shows an upright engine with a reduction means for driving the propeller. The rear mounting 5 is above the crankshaft 2; the center of the cross member I locates the axis of oscillation 3, and the axis of oscillation 3 is substantially parallel with the crankshaft 2. This parallel location of crankshaft and axis of oscillation may be obtained in an inverted engine, such as shown in Figure 3, if desired, by locating the reduction means I6to extend downward from the crankshaft 2, instead of upward above the crankshaft as shown in Figs. 3 and 4, as anyone versed in the art will understand. Such a change will locate the axis of oscillation below the crankshaft and substantially parallel to the crankshaft. Whether an upright or an inverted engine is employed, it is thought that the axis of oscillation substantially parallel to the crankshaft is to be preferred over geared constructions in which the axis of oscillation is at a greater angle to the crankshaft.

Fig. 5 shows an upright engine such as shown in Figs. 1 and 4 but with a downwardly extending reduction means. In this construction the rear mounting 5 is above the crankshaft and the axis of oscillation is at an angle to the crankshaft.

late in perfect balance and there is no bodily transverse movement of the propeller due to this balanced oscillation, nor is there bodily transverse movement of the engine due to this balanced oscillation. The exact amount of this oscillation is of little importance and hence a desired amount of oscillation may be employed to eliminate perfectly vibrations resulting from explosive torque reactions.

Fig. 6 shows a front view of the cross member I. The two halves are bolted together by the bolts and nuts I and they clamp about the rubbers II, to which is vulcanized or otherwise properly attached, the inner metallic sleeve I8. If desired, the rubbers I! may be cut through on one side, then slipped over the sleeves I8 and the cross member I then bolted in place about the rubbers II. In any case the result will be the same, in that the cross member I is properly cushioned by the rubbers l1, l1.

Figs"? and 8 show details of the rear rubber and pivotal mounting, which is composed of:

1st: The inner metallic sleeve I3, adapted to fit over the rear cylindrical portion of the engine extension 8 and rotatable with respect thereto. This operates with the extension 8 to provide a pivotal mounting that positively locates the axis of oscillation. 2nd: The cushion member I4; and 3rd: the outer metallic sleeve I5. The sleeve I5 is adapted to fit in the rear mounting framework support, which will be explained more in detail when describing Fig. 15. The sleeve I5 is not absolutely. necessary for the proper operation of the rear mounting, but for quick installation and removal of the rear mounting, the sleeve I5-should be used. A set screw (not shown) is used to prevent the rotation of the sleeve I5; or any other proper means to prevent its rotary movement and resulting wear may be employed.

It will be seen that the metal bearing provided by the extension 8 and the sleeve I3 insures that any oscillation at the rear of the engine will take place exactly about the axis 3. Hence, at both ends, the engine is forced to oscillate at all times about the proper axis 3, in perfect bal-- ance. It will be noted that in this construction no torque is taken at either the front or the rear mounting, the torque being taken entirely by the torque spring I I. I

Fig. 9 shows a rear mounting which is adapted to take torque through the rear mounting 5. The inner sleeve i3 is splined and is adapted to fit over a rear extension 8' of the engine that has been splined to fit the sleeve I3'-. The rubber cushion I4 is vulcanized or otherwise properly fixed to the sleeve I3 and to the outer ,plined sleeve I5.

Fig. 10 shows a sectional view of the torque taking rear mounting when in place and when provided with additional torque taking means. The outer splined sleeve, I5 is fitted into the splined opening in the shell I9 of the rear mounting framework support, which is supported on the plane framework or fuselage by the members 28 or otherwise. This construction, as described so far, will take torque through the rear mounting to the plane, but will not take the thrust or pull of the propeller. If the proper splines are provided this Fig. 9 mounting may be used to take torque at the front mounting.

If it is desired to take the thrust also through the rear mounting to the plane, the locking collar 2I is screwed into the support shell I9 and the collar 22 is screwed upon the rear extension 8' "pins as shown or otherwise. With this construc-,

tion the rear mounting transmits both the torque and the thrust from the engine to the plane framework.

Fig. 11 shows one form of torque spring II, which is to be attached by wrist pins to the engine at one end and to the plane framework at the other end.

Fig. 12 shows a view from above of one form of framework for mounting the front end of the engine on the plane. The feet 23,23, 23, 23, are bolted or otherwise properly mounted upon the plane. Any other proper design of framework to accomplish the same ends may be used. The sleeves I8, I8 (Fig, 6) of the cross member 1 fit over the support members 24, 24. If the torque spring I I is alone relied upon to locate the engine longitudinally, the nuts 25, 25, may be left off, or they may be locked in place when spaced forward from the sleeves I8, I8, of the cross member I, so as to act only in a safety capacity. If, however, the spring II, or other means is not relied upon to locate the engine longitudinally, the nuts 25, 25, are to be screwed up to contact the sleeves I8, I8, and then cotter pinned in place.

Fig. 13 is a section of Fig. 12 on the center line shown. Rubber cushions such as indicated at 23' may if desired be used to mount the feet 23, upon the plane.

Fig. 14 shows a metal brace 21 to hold the two halves of the framework together so that each may support the other. The brace 27 is to fit over the members 24, 24, and is to be held thereon by the nuts 25, 25, of Figs. 12 and 13. This brace 21 may be used in addition to, or in place of, the brace 26 which in Figs. 12 and 13 is shown as an integral part of the framework.

Fig. 15 shows the rear mounting support framework to receive the plain rear mounting shown in Figs. 7 and 8. If the splined rear mounting shown in Fig. 9 is to be used, the shell I8 is splined to receive it, as shown in Fig. 10. And if thrust is to be taken, threads are provided to receive the collars 2I. I

Figs. 16 and 1'7 show two views of an adjustable hydraulic resistance to the torque ycushloning oscillation of the engine unit. The lever 28 is properly attached to the rear cylindrical portion or extension 8 of the engine unit and has the ball-jointed connection 29 with the rod 30. A rubber connection may be used at this point in place of the ball-jointed connection shown, provided it will give the required universal connection. If a certain resiliency is desired combined with the hydraulic resistance, the lever 28 may be constructed of a leaf spring 28' properly connected by ball joint 28 or rubber connection, to the rod 30' (see Fig. 17). The leaf spring 28 may be attached at any other point to the engine unit and connected by rubber or other proper means to the engine supporting framework of the plane.

The rod 30 is provided with the properly constructed hydraulic piston or plunger 3|, adapted to reciprocate in the hydraulic cylinder 32, which is filled with proper hydraulic liquid such as glycerine or oil or a proper mixture of different liquids. The two ends of the cylinder 32 are connected by a duct or channel 33. When the piston 3| moves up and down in the cylinder 32, the liquid displaced by the piston 3I may move from one side of the piston 3'I to the other side thereof through the duct 33. Preferably the cylinder 32 is attached properly to a rubber base 38 which tions.

in turn is attached to a base 39, which base 39 is properly attached to the airplane through framework or other proper means. The rubber base support 38 and the ball or rubber connection between the rod 30 and the arm 28 permits the slight movements of the device that are necessary as the arm 28 moves with the oscillation of the engine unit. When the duct 33 is wide open, the hydraulic device does not materially resist the oscillation of the engine unit,

When the duct 33 is closed tight, either by the manually operated adjusting valve 34 or the valve 35, no liquid can flow through the duct 33 and the movement of the piston 3'1 will be prevented, and hence the oscillation of the engine unit will also be prevented. That is, the hydraulic device may either provide no restriction at all to the oscillation, or may entirely prevent oscillation of the engine unit, depending upon how it is adjusted. The valve 34 is to be manually operated at any time desired or necessary, to provide any result intermediate these two extremes. The valve 35 is to be set as desired and so locked by the split lockable lever 36. A rod 31 connects the lever 36 with the throttle All of the plane, the connection being such as to provide the adjustment desired fOr the valve 35 at different throttle locations. When this interconnection between the throttle 40 and the valve 36 is properly set, it is left as set; any additional adjustment required is then made at any time desired, by the valve 34. hydraulic means may be employed, if desired.

The idea of this hydraulic means to resist the oscillation of the engine unit, is that it may tend to dampen out certain vibrations at certain speeds or throttle openings, and also to assist the inertia of the engine unit in the control of the oscilla- At low speeds, such as when starting, or stopping the engine, and when for any reason the explosions do not follow each other as quickly as when the engine is going at a higher speed, the explosions may tend to force engine oscillations of extreme amount. When the engine is up to a higher speed the inertia of the engine and the short space of time between explosions tends to automatically cut down this amplitude of oscillation.

In any case, and at any time, if there 1s the slightest feeling of vibration, the hydraulic means may be adjusted one way or the other to soften this vibration. Also, and perhaps more important, if for any reason, like a broken or dirty spark plug or other cause, one or more cylindersbegin to miss, or for any other unusual reason vibra-.

tion occurs, the addition of the hydraulic resistance may be used to cut down the amplitude of the oscillation, or even eliminate it, and thereby reduce the vibration; for if oscillation for any reason is not taking place in perfect balance, it should be reduced in amount so as to reduce the "vibration. Two or more levers 28 and co-acting parts may be used for this purpose, if desired.

In this hydraulic device, though a straight moving piston is shown, a rotary type (well known in the trade) may be employed if desired; and in place of the frictional resistance of the liquid through the adjustable opening of the duct 33, the frictional resistance of any surface to surface means, with adjustable force of contact between the surfaces, may be employed if desired. But, in any case, the result is that the torque cushioning resistance may be accomplished by the addition of means that tend to dampen the Any other proper design or type of retically most perfect results, I prefer that neither.

front nor rear mounting take either torque or thrust, still, I know that with properly built and balanced engines, and where such theoretically perfect results are not of the greatest importance, it may be possible to take some or all of either torque or thrust, or of both torque and thrust, on either the front or the rear mounting, or both front and rear mountings may take either torque or thrust or both torque and thrust. In any case and with any construction, in engines whose center of mass does not lie in the crankshaft axis, or in engine units havin the center of mass of the propeller at a different level than the center of mass of the engine, or at a different level than the crankshaft axis, or in fact with any cylinders-in-line engine construction, the axis of oscillation must pass through both the center of mass of the propeller and the center of mass of the engine.

I realize that in some types, kinds, sizes and designs of engines, in which the center of mass is not normally in the crankshaft axis, it may even be possible to so design as to re-distribute the weights of different parts of the engine itself, or distribute the weights of accessories or attachments, such as starter, supercharger, battery (if mounted as a unit with the engine) silencer, air cleaner, or thelike, so that the center of mass of the finally completed engine will lie in the crankshaft axis. Such re-design of the complete engine, instead of avoiding this invention, will only tend to make more perfect results, when this invention is employed. In any case, when the axis of oscillation thus passes through the center of mass of the propeller and through the center of mass of the engine, regardless of their locations, the torque cushioning oscillation of the engine can produce no vibration thatis due to mass movement of the propeller, or that is due to mass movement of the engine.

It may be well to explain, even for those skilled in the art, just how the location of the rear mounting may be quickly and accurately arrived at, for either a radial or an in-line engine, and with a certain and correct final result.

'A plumb bob is first suspended from a strong, stationary and elevated point of support, and the floor is carefully and accurately marked just below the point of the plumb bob. Though any other means or method for properly locating the floor point vertically below the point of support (such as a surveying instrument, for instance); may be employed, it is thought that the use of a plumb bob is the simplest and most reliable method.

After the accurately located mark on the floor is properly established, a complete engine and propeller unit, in. the condition in which it will be operated, is then hung from the center of the propeller hub by light flexible wire or cable or proper universal joint means, from this same point of support; and with the engine and propeller unit thus hanging, the center of the rear mounting should then be located directly above the marked floor point. This method makes certain that the axis of oscillation will pass through the center of mass of the propeller, the center of mass of the engine, and the center of the rear mounting. The front mounting should then be located concentric with a line connecting the center of the rear mounting and the center of the propeller hub, that is, the center of mass of the propeller.

The above explanation will be sufficient for anyone skilled in the art to properly locate the mountings to provide the correct axis for balanced oscillation. Balanced oscillation in an engine unit is just as important as balanced rotation in a flywheel.

Even in a radial engine, if the center of mass of the engine is not directl in the crankshaft method will show that most radial engines, even I those that may be thought to have the center of mass in the crankshaft axis, actually do not have the center of mass exactly in the crankshaft axis.

This suspension method of arriving at the proper location for the rear mounting such that the axis of oscillation will pass through the center of mass of the propeller and of the engine, though perhaps one of the simplest, is one of the most important points of novelty in this invention.

The center of mass of the propeller positively locates the front mounting as concentric thereto, and the front mounting and the center of mass of the engine combine to positivel locate the axis of oscillation that will provide balanced .oscillation of the entire engine and propeller unit.

The front mounting and the center of mass of the engine do not locate the rear mounting position unless the floor point is properly marked vertically below the point of support, and the engine and propeller unit later hung like the plumb bob so that the location of the rear mounting may thus be obtained from the floor point.

The reason for such extreme care in mounting an airplane engine so it will oscillate in perfect balance should perhaps be more full ex plained.

For reasons that are not necessary to consider here, the maximum speed of a propeller is generally kept fairly close to a maximum of 2000 to 2300 revolutions per minute. Thus, if the propeller is not geared, the maximum engine speed is limited, and hence the maximum power output of the engine is limited.

If an engine is properly designed for the speed, it will, however, deliver twice as much power at 4000 revolutions per minute, as at 2000 revolutions per minute. (Automobile engines have been driven even as fast as around 7000 revolutions per minute.) But, with such an increase of speed, the engine vibration has an increased deteriorating effect upon the plane, causing an increase of flaws and ruptures and breakage of parts.

However, if the engine can be mounted so that its vibrational forces will not be transmitted to the plane, increased engine speed may provide a plane with perhaps twice the power from substantially the same weight of engine, due to the increased engine speed when a propeller gear drive is used. In other words, if a plane with a 1000 horse power engine has a certain performance, the same plane will have very greatly improved performance if the propeller is eared one to two, and the engine is then driven at twice the speed so it will deliver 2000 horsepower. Of course, a near perfect engine mounting would have to be provided, and a larger capacity propeller used, so that twice the engine power will drive the larger capacity propeller at substantially the same speed. So far, however, geared propellers have not been universally adopted for planes, and those that are now geared, are geared to run the engine a only about 1 times the propeller speed. It is thought that running the engine at double the propeller speed is not now broadly done because of resulting trouble in the plane due to engine vibration.

The higher speed of the engine vibration in the plane, even though the amplitude of the vibration may be less as the speed increases, would be more destructive than a lower speed of vibration. Therefore, the closer to perfectly vibrationless engine performance that can be obtained, the better. It is for these reasons that extremely accurate mounting of an airplane engine unit is of very great importance.

In the drawings various propeller positions are illustrated with the propeller driven from the engine through gears or other reduction means. The case where the reduction means employed leaves the propeller in the same or substantially the same relative position as when no reduction means is used, that is, concentric with the crankshaft, is not illustrated in the drawings, but anyone skilled in the'art, it is thought, will not need such additional illustration for complete understanding.

It is thought that in many cases a substantially unchanged position of the propeller, even though it is driven through reduction means, will be preferable. That is, with the propeller sub stantially or entirely concentric with the crank-' shaft. However, the drawings illustrate sufficiently how to mount the engine with-various changed positions of the propeller due to the use of reduction drive means.

I claim:

1. In an airplane engine and propeller unit the propeller being rigidly mounted upon a revolving shaft carried by the engine and providing the load for the engine, and the engine case being normally un-counter-weighted, a cross member pivotal support pivotally supporting the end of the engine adjacent the propeller and located concentric with said propeller, cushion means supporting said pivotal support on the airplane, and means mounting and locating the end of the engine unit opposite said propeller on the airplane for adjustably opposed and automatically controlled oscillatory movements, said mountings forming an axis of oscillation for the engine and propeller unit located to pass through the center of mass of the propeller and through the center of mass of the engine.

2. In an airplane engine and propeller unit, a propeller mounted on said unit to revolve at'a different speed than the speed of the engine, driving means connecting the engine crankshaft and the propeller to drive the propeller at a different speed than the speed of the engine, a cross member pivotal support pivotally supporting the end of the unit adjacent the propeller and located concentric with said propeller, cushion means supporting said pivotal support resiliently on the airplane at remote points, and means mounting and locating the end of the engine unit remote from said propeller on the airplane for resiliently opposed oscillatory movements of the said unit in balance.

3. In an airplane engine and propeller unit mounting, a propeller, a crank-shaft, front and rear mounting means to resiliently support said engine and propeller unit in an airplane for resiliently resisted torque cushioning oscillation about a longitudinal axis, and located to position said axis to pass through the center of the hub of the propeller and the center of mass of the engine, one of said mountings including means attached to the said unit, and an engine speed control, and variablycontrolling torque Oscillation of the said unit.

4. In an airplane engine and propeller unit, a propeller mounted on said unit, an engine, a crank-shaft for driving the propeller, front and rear mountings, at least one of which is in the form of a pivotal metallic cushion support, a framework carried by the plane on which the support is held, and means for taking the thrust through the rear mounting to the plane whereby said rear mounting transmits both the torque and the thrust from the engine to the framework of the plane. a

5. In an airplane .engine and propeller unit, a.

propeller mounted on said unit, a cross member pivotall supporting the end of the unit adjacent to the propeller and located concentric with said propeller, cushion means supporting said pivotal support resiliently on the airplane, and means mounting and locating the end of the engine unit remote from said propeller on the airplane for resiliently opposed oscillatory movement of the said unit in balance.

6. The combination of an airplane engine and propeller unit, a propellerdriven by the engine crank-shaft, mountings carried by the airplane and afiording an oscillatory support at opposite ends of the engine along an axis of oscillation extending through the center of the hub of the propeller and through the center of mass of the engine, and automatically adjusted, frictional means attached to and controlling the oscillatory movement of the said engine unit.

7. The combination of an airplane engine and propeller unit, a propeller driven by the engine crank-shaft, mountings carried by the airplane and affording an oscillatory support at opposite ends-of the engine along an axis of oscillation extending through the center of the hub of the propeller and through the center of mass of the engine and the center of the front and rear mountings, and hydraulic means limiting torque oscillation and controlled by an engine speed control.

ROLLAND S. TROTI'. 

